ESF Researchers Focus on a Tiny Tanzanian Toad

Kihansi spray toads extinct in wild7/19/2011

A species of tiny toads, which quickly became extinct in the wild after it was discovered in Tanzania, is thriving in a laboratory at the SUNY College of Environmental Science and Forestry (ESF).

ESF scientists are studying the Kihansi spray toads in an effort to find ways to safely reintroduce the animals to the Kihansi River Gorge in southeastern Tanzania.

"This is a species that's extinct in the wild but it's right here in Syracuse," said Dr. James Gibbs, an ESF conservation biologist. "This species, without the help of captive breeding, will go extinct. It's part of the natural heritage of Tanzania."

The Kihansi spray toad was discovered in 1996 in conjunction with the construction of a dam on the Kihansi River. A population of the toads was found living near the bottom of a waterfall where the river plunged more than 3,000 feet.

The toads lived in a nearly vertical wetland created by the forceful spray that came off the pounding water. Gibbs compared the environment to living next to an open fire hydrant.

"There was a unusual species of amphibian found there," he said. "And after much searching, it turned out to be a truly endemic and unique species. They have never been seen anywhere else. It might be the four-legged vertebrate species with the smallest range in the world."

Construction of the dam resulted in reduced spray in the toads' habitat and their numbers quickly declined. Some 500 of them were removed to the Bronx Zoo and the Toledo Zoo, where staff members habituated them to captivity and got them to reproduce. After dwindling to about 50 individuals, the captive population has rebounded.

The Tanzanian government would like to reintroduce the animals but they want to be sure the environment has been stabilized enough to provide a suitable habitat.

"That's where we come in," Gibbs said.

Scientists are concerned about how a returned toad population might be affected by pesticides in the river, particularly endosulfan from upriver agriculture, and the chytrid fungus that is harming amphibians worldwide.

"Nobody wants to put lots of toads back if they're going to suffer and not succeed in the restored habitat," Gibbs said.

In an agreement with the National Environment Management Council of Tanzania, Gibbs and his team are researching the effect of the fungus and the pesticide, both together and separately, on the toads.

The lab work is done by ESF undergraduate Chelsae Radell of Camden, N.Y, and graduate student Brooke Reeve of Waverly, N.Y.

"I like doing this because I'm doing something important for conservation," Radell said. "We're making an impact. The results of our study will help determine if this species can go back into the wild."

"I was always interested in amphibians," Reeve said. "Amphibians are kind of unsung in that they're a big part of the food web."

The students are caring for about 580 toads in the ESF lab, where visitors quickly learn contamination from the chytrid fungus is a huge concern. Anything that touches the floor, including shoes, gets a bleach bath upon entering and leaving.

"The reason the Kihansi spray toad has gone extinct in the wild is because of human impact," Radell noted. "I think if humans are causing their extinction, then everyone should care a little bit."

All amphibians play an important role in the environment, according to Reeve. "They're a major prey item. They also take care of a lot of insects. They are really linked into that food chain."

The animals are unusual among amphibians in that they give birth to live young and carry their babies on their backs. Kihansi toads range from 1 to 1.5 inches in length and weigh no more than a few grams. They feed on insects and other small invertebrates.

The toads illustrate the need to preserve individual species, Gibbs said. He pointed out that in the same gorge, scientists found a wild species of coffee that had not been seen before.

"That makes people say, 'Aha! Maybe saving species is worthwhile after all,'" said. "Also we need to find ways to get the species back into the wild because we can't pay forever to keep this toad in captivity. We need people to look after it and feed it everyday. If we can bring it back in the wild, it will take care of itself."